test-sequential-access.c

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define PROGRAM_NAME "testwidths"

#define MAKE_TEST(type, name)          \
int name(int n, int v)                 \
{                                      \
        int i;                         \
        int r;                         \
        type *x;                       \
                                       \
        x = malloc(n * sizeof *x);     \
        if (x == NULL) {               \
                fprintf(stderr, "Memory allocation failed!\n"); \
                exit(1);               \
        }                              \
        for (i = 0; i < n; i++)        \
                x[i] = v;              \
        r = 0;                         \
        for (i = 0; i < n; i++)        \
                r += x[i];             \
        free(x);                       \
        return r;                      \
}                                      \

MAKE_TEST(char, char_test);
MAKE_TEST(short, short_test);
MAKE_TEST(int, int_test);

void print_usage_and_exit(int errcode)
{
        fprintf(stderr, "Usage: %s <char|short|int> <numelems> <value>\n",
                PROGRAM_NAME);
        exit(1);
}

int main(int argc, const char **argv)
{
        int usetype;
        int numelems;
        int val;
        int r;
        if (argc != 4)
                print_usage_and_exit(1);
        if (strcmp(argv[1], "char") == 0)
                usetype = 0;
        else if (strcmp(argv[1], "short") == 0)
                usetype = 1;
        else if (strcmp(argv[1], "int") == 0)
                usetype = 2;
        else
                print_usage_and_exit(1);
        if (sscanf(argv[2], "%d", &numelems) == 0) {
                fprintf(stderr, "Integer conversion of %s failed\n", argv[2]);
                print_usage_and_exit(1);
        }
        if (sscanf(argv[3], "%d", &val) == 0) {
                fprintf(stderr, "Integer conversion of %s failed\n", argv[3]);
                print_usage_and_exit(1);
        }

        if (usetype == 0)
                r = char_test(numelems, val);
        else if (usetype == 1)
                r = short_test(numelems, val);
        else if (usetype == 2)
                r = int_test(numelems, val);
        else
                assert(0);

        printf("%d\n", r);
        return 0;
}

Testing simple sequential access of integers of different sizes.
Times below 10M integers were too small to be reliably measured.
Run-script:

#!/bin/bash
for n in 10000000 100000000; do
	for t in char short int ; do
		for i in `seq 10` ; do
			echo -n "Run $n $t $i: "
                        TIMEFORMAT='%U s'
                        { time ./test "$t" "$n" 1; } 2>&1 1>/dev/null
		done
	done
done

Results on my machine (AMD-X2 250, gcc -O2)

Run 10000000 char: 0,020 s
Run 10000000 char: 0,028 s
Run 10000000 char: 0,012 s
Run 10000000 char: 0,020 s
Run 10000000 char: 0,016 s
Run 10000000 char: 0,020 s
Run 10000000 char: 0,016 s
Run 10000000 char: 0,016 s
Run 10000000 char: 0,020 s
Run 10000000 char: 0,024 s
Run 10000000 short: 0,028 s
Run 10000000 short: 0,016 s
Run 10000000 short: 0,028 s
Run 10000000 short: 0,028 s
Run 10000000 short: 0,016 s
Run 10000000 short: 0,028 s
Run 10000000 short: 0,024 s
Run 10000000 short: 0,024 s
Run 10000000 short: 0,020 s
Run 10000000 short: 0,024 s
Run 10000000 int: 0,020 s
Run 10000000 int: 0,024 s
Run 10000000 int: 0,028 s
Run 10000000 int: 0,016 s
Run 10000000 int: 0,028 s
Run 10000000 int: 0,032 s
Run 10000000 int: 0,024 s
Run 10000000 int: 0,020 s
Run 10000000 int: 0,016 s
Run 10000000 int: 0,024 s
Run 100000000 char: 0,156 s
Run 100000000 char: 0,180 s
Run 100000000 char: 0,176 s
Run 100000000 char: 0,176 s
Run 100000000 char: 0,196 s
Run 100000000 char: 0,176 s
Run 100000000 char: 0,152 s
Run 100000000 char: 0,168 s
Run 100000000 char: 0,184 s
Run 100000000 char: 0,168 s
Run 100000000 short: 0,192 s
Run 100000000 short: 0,200 s
Run 100000000 short: 0,196 s
Run 100000000 short: 0,216 s
Run 100000000 short: 0,192 s
Run 100000000 short: 0,188 s
Run 100000000 short: 0,204 s
Run 100000000 short: 0,184 s
Run 100000000 short: 0,220 s
Run 100000000 short: 0,200 s
Run 100000000 int: 0,180 s
Run 100000000 int: 0,216 s
Run 100000000 int: 0,192 s
Run 100000000 int: 0,216 s
Run 100000000 int: 0,236 s
Run 100000000 int: 0,236 s
Run 100000000 int: 0,232 s
Run 100000000 int: 0,216 s
Run 100000000 int: 0,208 s
Run 100000000 int: 0,244 s

Averages:

Avg 10000000 char: 0.0192
Avg 10000000 short: 0.0236
Avg 10000000 int: 0.0232
Avg 100000000 char: 0.173
Avg 100000000 short: 0.199
Avg 100000000 int: 0.218